Green fluorescent carbon dots for sensing of quercetin and pH and cell imaging

Green fluorescent carbon dots (G-CDs) were fabricated from Coptis chinensis directly via one-step hydrothermal treatment for the determination of quercetin (QCT) and pH sensing. The obtained G-CDs have low cytotoxicity, good photostability and excellent water solubility. The optimal excitation wavelength and emission wavelength were 480 and 530 nm. A remarkable emission reduction displayed when QCT was added to the G-CDs and the linear detection range is 0-200 μM, the limit of detection is 4.41 nM. The proposed method was applied to the determination of QCT in Haerbin beer products with satisfactory successful recovery. Furthermore, the G-CDs exhibited sensitive changes to pH and two fluorescent pH sensors in the linear ranges of 2.0-6.0 and 6.0-11.0 were constructed based on this. They also provide a feasible method to measure the pH value of real water samples. Importantly, the fluorescent sensor has been extended to detect QCT in yeast cell, demonstrating the G-CDs present potential biosensing application prospect.